Let's dive into this subtraction. We'll start with 801039 and subtract 17809 from it.

Step 1: We'll start by subtracting the digit 9 and the borrow 0 from 9 in column 1 and get 0.
0 is the first digit of our result.

Step 2: We'll start by subtracting the digit 0 and the borrow 0 from 3 in column 2 and get 3.
3 is the next digit of our result.

Step 3: We'll start by subtracting the digit 8 and the borrow 0 from 0 in column 3 and get -8.
We add -8 to 10 and get 2 as the next digit of the result.

Step 4: We'll start by subtracting the digit 7 and the borrow 1 from 1 in column 4 and get -7.
We add -7 to 10 and get 3 as the next digit of the result.

Step 5: We'll start by subtracting the digit 1 and the borrow 1 from 0 in column 5 and get -2.
We add -2 to 10 and get 8 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 8 in column 6 and get 7.
7 is the next digit of our result.

So, 801039 - 17809 = 783230.